The present invention relates to scraper blades which are used to remove residual material clinging to the return run of a conveyor belt. It has been known in the prior art to provide either linearly or radially adjustable scraper blades. Radially adjustable scraper blades have had one disadvantage as compared with the linearly adjustable scraper blades in that as the blade of a radially adjustable scraper wears, and is adjusted accordingly, the angle between the conveyor belt and the scraper blade changes. While different cleaning angles may be found to be more desirable for differing situations, it is apparent that a radially adjustable scraper blade will operate with an optimum cleaning angle for only a small part of its life. Scraper blades which are radially adjustable are shown in U.S. Pat. Nos. 4,098,394, 4,359,150, 4,586,600 and 4,643,293. Scraper blades which are vertically adjustable are described in U.S. Pat. Nos. 4,249,650 and 4,696,389. Scraper blades which utilize a curvilinear shape are shown in U.S. Pat. Nos. 4,269,301, 4,489,823, 4,658,949 and 4,787,500. However, the prior art does not disclose a radially adjustable scraper blade having a curvilinear scraping surface configuration which maintains a constant cleaning angle with the conveyor belt as the scraper blade is adjusted radially.